In my constant researching thru the internet I have found several instances of people saying snails can carry the "camallanus worm"

Funny how when you do specif searches for such things you never can seem to find anything related to what your looking for, Anyways I just thought of this post and figured maybe I'd mention this, in case others may wonder,

I'll have to see iffin I can't relocate some of those sites and post them..

It makes me wonder if they are confusing it with the angiostrongylus cantonensis.

Pomacea and Marisa species have been introduced in Africa and Asia to control snails (Planorbidae: Bulinus sp. and Biophalaria sp.), which serves as intermediate host for trematoda parasites. These parasites can cause swimmers itch and schistosomiasis, a disease that affects over 200 million people in tropical regions. Despite the fact these tremadote parasites do not complete their life cycle in apple snails, apple snails themselves can carry these parasites and nematodes of the genus Angiostrongylus. Angiostrongylus cantonensis can afflict humans and cause eosinophilic meningoenchephalitis. One of the species was introduced as bio-agent is Marisa cornuarietis . This apple snail competes with other snails and predates on them.

Most of the snails that are sold in the pet trade are so many generations away from the "wild" that even these parasites would be uncommon. Here's a link that Stijn put up about snails and parasites:

Camallanus is a nematode that usually requires an intermediate host to reproduce. I have confirmed that common ramshorn snails can act as a host. I'm not sure about apple snails, but I suspect they can. The worm is not visable at the stage it would be in the snail. The snail simply contributes to the eggs hatching and then expels the tiny worms which are eaten by fish (as they mouth through debris). It is at this point they grow into the adult worm inside the fish.

By your own experimentation, or is there a source where you read this? I have not seen snails mentioned when reading about possible intermediate hosts of this particular genus of worm, but that may be because the papers I have seen are not addressing the entire host range for the Camallanus genus (vs. the range for specific species, which seems to be more commonly described).

It was from an experience I had which was very straight forward. Many years ago, I had in infestation of these worms in my quarantine room. After reading that many species required an intermediate host, I noticed that the only tanks with a problem was those with snails. Once I removed the snails, the camallanus problem went away (had to dispose of the infected fish also). New fish put into these tanks, did not come down with the nematode. Since reproduction produces many thousands of eggs, re-infestation should have taken place if they were in the tanks. I was not medicating at the time, since this particular worm was amazingly tolerant of any meds I had tried in the past.

This may be attributed to some amazing coincidence, but I'm pretty convinced it's true for at least some species. Since there are many species, it probably does not hold true for all of them.

If it wasn't a controlled experiment checking one cause at a time, about the best one can say is that it warrants further investigation, not that it is confirmed. Based on what I've read of the life cycle of the worms (regarding fish-to-fish life cycles), there are enough variables in your situation that it doesn't seem conclusive, paritcularly if the infected fish were removed shortly after or before the snails.

I wasn't trying to give the impression that it was a scientific experiment or confirmed, just that I was convinced. I've spent enough time over a microscope looking at nematode eggs, to know that they lay them by the many thousands at a time and they readily infect any fish in the tank for quite awhile after the fish are removed. The eggs of most nematode species are quite resistant to medications and survive for along time enabling them to infect the host fish very readily. However, the larvel form can be killed quite readily before it gets into the fish. The camallanus infection in the fish in these tanks was extreme. Every fish, had guts full of worms. This includes my own clean fish that were added to the tanks and became infected after that. Hard for me to believe that the new stock would not become infected after the snails were removed or the tanks without snails never showed any sign of infection (150 aquariums, side by side, same siphon, same nets, etc) . I treated the infected tanks with a heavy dose of formaldehyde/malachite green before the introduction of the new fish, which seems to have been enough to kill any nematode larva.

What I think people should understand is that no matter what happened in my situation, the species they have could have a different life cycle. Just realize that snails may act as an intermediate host.

I wasn't trying to give the impression that it was a scientific experiment or confirmed, just that I was convinced.

This may seem like nitpicking, but it's important to always make it clear where your conclusions are coming from as well as the degree of formality in the observations, since there is often a lot of conflicting anecdotal information floating around regarding invertebrate parasites. From what you've posted so far, it's clear that the worm problem disappeared when several things happened at once: snails were removed, fish were removed, and chemicals were added. This does mean that the snails are a possibility due to correlation. However, the other two events are also possibilities unless there was some significant time delay between environmental changes to rule them out. It still seems to be an untested hypothesis as far as the original question in the thread goes.

The most compelling evidence to support my view is the fact that only tanks with snails became infected and every tank with snails became infected and every fish in them was infected (probably around 30 infected tanks out of the 150). These tanks were side by side with the many tanks that did not have any sign of the infection (fecal and intestinal smears confirmed this). I know how easy it is to spread these worms from tank to tank with nets, siphons, etc., yet it did not spread over an 8 month period. In the absence of controlled experimentation, this is pretty strong evidence to support my guess. In my view, almost an impossibility that the snail did not act as an intermediate host. And yes, these are the facts in my situation.

If you are uncertain of the species, are you sure these were actually from the genus in question?

I know how easy it is to spread these worms from tank to tank with nets, siphons, etc., yet it did not spread over an 8 month period.

This would actually suggest that transportation by equipment is not a good way to spread the stage responsible for infecting new fish (for the particular worms in your tanks anyway), at least with whatever method you use for your equipment. I don't know if you do cleaning dunks with everything between tanks, even just using clean water, but doing so would certainly decrease the chance of parasite transfer.

only tanks with snails became infected and every tank with snails became infected and every fish in them was infected

Were these tanks completely devoid of all other invertebrates, including other worms, copepods, ostracods, etc? It's not uncommon for other small organisms ride in on snails by accident*, and those are some other hosts I have seen cited for the Camallanus genus.

In the absence of controlled experimentation, this is pretty strong evidence to support my guess.

Forgive my skepticism (obviously I was not witness to the event and it would require time-travel to fill in all of the information gaps), but similarly casual correlation-based observations are also commonly used to assert that snails are carriers for other fish parasites like ich. The issue will still have to be an open question here until someone either tests it or digs up a paper/other document that can fill in the gaps without assumptions.

----

*EDIT: I should also note that there is also a type of worm that I have seen living inside the mantle cavity of Planorbids that did not appear to be parasitic. Although I can't recall ever having identified those worms, some sources do point to other worms as intermediate hosts for certain Nematodes (such as http://edis.ifas.ufl.edu/pdffiles/fa/fa09100.pdf - although not addressing Camallanus specifically).